1. Technical Field
The present invention relates to a lubrication structure for a rocker arm.
2. Related Art
Conventionally known valve gears for internal combustion engines include a rocker arm which is rocked about a cam shaft. One of two ends of the rocker arm is engaged with an upper end of a valve stem of an exhaust or intake valve and the other end of the rocker arm is engaged with a cam, so that the rocker am is rocked by a cam action, whereby the valve is opened and closed. Japanese Patent Application Publication No. JP-A-H05-248211 discloses a valve gear including one of the rocker arms of the above-described type.
In the disclosed valve gear, an adjusting screw is screwed into a valve stem side end of the rocker arm. The adjusting screw has a lower end which is rotatably supported in a receiving member provided at the valve stem side. Furthermore, since the adjusting screw and the receiving member are in a relation that both are rubbed against each other, lubrication oil needs to be supplied to a rotatable support portion between the adjusting screw and the receiving member. For this purpose, in the above-described conventional technique, a lubrication oil hole is axially formed through the adjusting screw so that lubrication oil is supplied through the oil hole to the receiving member.
In the above-described lubrication structure, however, since an oil hole for lubrication has a small diameter, it is not easy to bore a hole with the small diameter so that the hole extends through the adjusting screw. This poses a problem.